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Friday, May 28, 2010

In a previous blog entry (Robotic Precusor Missions), I described a proposed new NASA initiative in the manned exploration program to develop key technologies and scout future locations for manned exploration. At that time, the program was pretty sketchy. NASA just held a conference on this program that begins to fill in the blanks. I want to emphasize, however, that the presentations are full of disclaimers stating that these are early plans likely to change. Congress also has to go along with the Administration's proposal and fund the programs, which is anything but certain.

If these programs are funded, they would be great news for planetary exploration. The entire program has many parts, and the full picture is too complex to describe here. Most of the programs are specific to manned spaceflight capabilities to reach near Earth asteroids and Mars. Two programs, however, directly bear on unmanned planetary exploration. This post will focus on the Robotic missions, and a subsequent post will focus on the technology development missions.

The role of the Robotic missions is to scout ahead of human exploration. To provide an analogy, the Apollo missions to the moon had the robotic Ranger, Surveyor, and Lunar Orbiters that scouted the terrain and provided essential information prior to human flights as well as fundamental scientific exploration. The in-progress Lunar Reconnaissance Orbiter and the recently completed LCROSS missions are modern versions of the same idea. NASA is proposing a series of missions in the $500-800M range that would scout near Earth asteroids, the moon, and Mars. This budget figure, which would include the launch vehicle, puts these missions in the class of Discovery missions. (The fully burdened cost of each Discovery mission appears to be about $800M, with ~$450M going to the PI for spacecraft and instruments.)

The mission profiles and instruments would be selected to answer key questions relevant to human missions. Is the surface safe to land on? Are there hazardous substances? Can we find resources to use? The missions that can answer questions like these can also provide good science and good vicarious armchair exploration.

The robotic precursor program appears to be quite ambitious. In addition to the major missions, several Scout missions costing less than $200M would also be flown. The presentation is vague about what these missions might do. The program would also fund individual instruments on scientific missions to make instruments useful for planning manned missions.

Example of how an investigation can approached from both the perspective of a precursor and a scientific mission. In many cases, the data collected for one will inform the other.

Current roadmap of precursor missions. xPRP missions would be $500-800M, MOOs are missions of opportunities that would usually pay to place an additional instrument on a science mission, and xScouts are small missions $100-200M in cost.

The slide above provides the current strawman list of missions under consideration. Here, I’ll expand on a couple of the missions. The 2014 near Earth asteroid mission would characterize one of these objects in terms of hazards, proximity operation conditions, and resources. The instrument list, though, reads like that of a scientific mission: sub-meter pixel imaging, LiDAR for topography, instrument(s) for compositional mapping, and radar for subsurface structural mapping. The mission would end with the spacecraft landing on the asteroid.

The 2016 Mars orbiter would leave for the Red Planet the same year as the Mars Trace Gas science orbiter. While the MTG orbiter would focus on atmospheric composition and dynamics, the precursor mission would focus on radiation hazards, near surface ice detection, potential landing site imaging, and radar imaging to peer beneath the surface dust. While these measurements would be essential to planning an eventual manned mission, all (except perhaps the in orbit radiation instrument) would address questions that have high scientific value for understanding Mars.

Additional large xPRP missions in the strawman roadmap include:

2015: Teleoperated Lunar Lander in a sunlit polar region and enhanced hydrogen signature to explore resources, hazards, and mission operations. Would include a Sojourner class rover. (Noted as being aggressive for budget allocation.)

2019: Near Earth Asteroid mission that is still to be defined but has a goal of including 3-6 spacecraft to explore multiple targets

Editorial Thoughts: If these missions fly, they would constitute a major program of scientific exploration. While no total budget is given, a quick back of the envelope calculation suggests that the program might be as large as $5B, or a little less than half the budget of the scientific planetary program. I suspect that the program is too ambitious for the projected budget. The lunar and Mars landers, for example, have the feeling of a New Frontiers class mission (>$1B with all costs included) rather than a Discovery class mission. I personally am most intrigued by the possibility of sending multiple smaller spacecraft to explore multiple near Earth asteroids and by the Mars orbiter. I suspect that others would find the two landers more intriguing.

The cynic in me, though, is skeptical. This program depends on the Obama administration’s proposed changes to the manned space program being accepted and funded by Congress. Right now, Congress seems to be somewhere between doubtful and hostile to the proposed program changes. It is possible that the Administration and Congress will compromise and keep elements of the old and new manned programs. New programs such as these precursor missions that don’t have established political constituencies and don’t keep existing workforces employed may not fare well.

I hope that I am wrong, but I will not get excited until I see these programs progress to hardware being built.

Tuesday, May 25, 2010

As with all my editorials, I am not trying to convince anyone to my point of view. No one on the Decadal Survey has ever heard of me, and my opinion counts for no more than any of the readers of this blog. Rather, I find that reading a good editorial (and I hope my efforts are 'good') helps me focus my own thinking and reach my own conclusions. So, with that in mind, here is one of the rare editorials on this blog.

In the next few months, the Decadal Survey will have to select missions to recommend for flight in the coming decade (2013-2022). We have already been warned that sticker shock is coming and that fewer missions can be flown than advocates and scientists would hope. At $3.2B and perhaps $4B with inflation and cost increases, the Jupiter Europa Orbiter would consume a substantial chunk of that ~$12-13B budget. (ESA's Jupiter Ganymede Orbiter, if selected, would be paid for out of Europe's budget for its next large science mission.) Perhaps most damning, funding EJSM would preclude funding for a flagship mission to Titan and Enceladus.

My first reason for favoring EJSM is that it would explore three classes of important objects: (1) icy moons that may be habitats of life either in our solar system or others, (2) a large gas giant that is our best analogue for the many gas giants found around other stars, and (3) an intense magnetospheres that serves as a surrogate for other such structures in the universe. The last two points speak for themselves, but I will expand a bit on the first point. I believe that the ultimate exploration of an icy moon environment will be at Titan, but that world has such active surface processes that untangling its geologic history will prove difficult. At Jupiter, we have four moons that provide case studies a range of tidally influenced moons (with Io and Callisto at the extremes) without the confusion of active surface processes. Finally, Europa may be a habitat for life, and we should explore that potential with a highly capable spacecraft.

My second reason for favoring EJSM is that the JEO mission is ready to fly. A decade of technology development and mission design has brought the mission to a point where risks are low. We learned last year in the shoot out between EJSM and the Saturn Titan System Mission (TSSM) that the same was not true for concepts to explore the Saturn system (click here for the orbiter and here for the in situ elements).

My final reason for favoring EJSM is the lesson learned from Mars exploration in the last decade. At the Red Planet, we have learned that a series of highly capable missions can together bring a deep insight into a world or, in the case of Jupiter, a system of worlds. NASA's JEO could be just the most capable of a fleet of craft that could also include ESA's Jupiter Ganymede Orbiter, Japan's magnetosphere orbiter, Russia's Europa lander, and possibly penetrators for Ganymede and/or Europa from another space agency. Together, this flotilla would do for the Jovian system what a decade of missions have done for Mars. What we learn from the Galilean moons will build towards our understanding of ice-ocean-rock moons including Titan and Enceladus.

Of these three arguments, I personally find the final most compelling. We have done most of the easy missions for the solar system. Significantly deepening our understanding of key worlds and systems will require focused exploration. (Even if JEO turns out to be the only mission to fly to Jupiter, it is capable enough that it would count in my opinion as focused exploration.) In the coming decade, I favor focused exploration on three and a half targets. First, there will continue to be Mars which is likely to receive several orbiters from Russia, China, and ESA/NASA, 2-3 rovers, and possibly a network of science stations. Second, could be the Jovian system. And third, there could be Venus which could be the recipient of Russian and American landers, a European balloon platform, and several orbiters. All in all, the next decade, thanks to the combined contributions of a number of space agencies, could see the in-depth exploration of the solar system expand from one target (Mars) to several.

The half target in my scenario would be the Saturn system. Eventually, we need to return there with flagship class spacecraft. I found the case laid out for a flagship class orbiter to take the global study of Titan to the next level in the TSSM study compelling. Not only will a battery of instruments be required, but a high power communications system (which drives the need for a flagship class spacecraft) is essential to return the data stream. However, there are, I think, a couple of low hanging fruits available for the Saturn system. The first is Enceladus, for which a New Frontiers-class mission with with advanced instruments should provide a significant advancement in our understanding. The second is in situ probes for Titan, which is about the easiest place in the solar system to land on or fly or float above. The proposals in progress for a Discovery-class lake lander and a Discovery-class airplane suggest that in situ Titan probes could be within the budgets and technical capabilites of several space agencies in the coming decade. The key problem for most in situ probes is the data communications challenge -- there simply isn't room within these probes to house the power systems and antennas to return large amounts of data. So, I favor a New Frontiers class orbiter that would switch between focused Enceladus studies and relay duties for Titan in situ probes over the course of perhaps a decade or more in orbit around Saturn.

For the past year, I have closely followed the Decadal Survey process as well as the planning processes of other space agencies. In this blog entry, I lay out the conclusions I've reached. I hope that the readers of this blog will lay out their own or challenge mine in their comments.

Sunday, May 23, 2010

A conference on the Europa Jupiter System Mission (EJSM) has just completed, and the presentations are a treasure trove of information on the proposed missions from three space agencies. (The presentation from the fourth, the Russian space agency, has not been posted.) The conference focused on the science questions and goals for these missions, and I recommend reading them (http://jakal.sp.ph.ic.ac.uk/EJSM/#Presentations)

This is the next to last post in a series that looks at the science of the EJSM missions (see Satellites, Jupiter, and Magnetosphere), with a focus on science other than that which would be done in orbit around Ganymede and Europa. In this post, I’ll summarize the proposal for penetrators for Ganymede and Europa. These are not the only lander concepts that are being investigated. A conference was held last year to discuss lander missions that range from a very large Russian lander to small hard impact landers and penetrators. I summarized these concepts in two blog posts (Russian Lander and Small Landers) or your can read the presentions at http://www.iki.rssi.ru/conf/2009elw/

At the more recent EJSM conference, presentations were given on the large Russian lander (not posted at the time I write this) and for a small penetrator that would be carried by the Jupiter Ganymede Orbiter and the Jupiter Europa Orbiter (see Europa Surface Element presentation). The penetrator would weigh just 15 kg with 1 kg for science instruments. The deorbit module for Ganymede would weigh 70 kg. After achieving orbit around its target moon, the orbiter would release the penetrator, the deorbit module would perform the deorbit maneuver and orient the penetrator for impact. Penetration into the surface would be a half to a full meter. Polar landing locations would provide optimum data relay opportunities since the orbiter would pass over the poles each orbit but over each equatorial location just twice twice for every revolution of the moon around Jupiter. Surface lifetime for the penetrator would be just two orbits of the moon around Jupiter (~7 days for Europa and ~14 days for Ganymede). [No explanation is given for why the Europa lander would not also operate for 14 days. It seems unlikely to be due to radiation; the penetrator will have already been subjected to intense radiation while still attached to the orbiter.]

The scientific goals for the penetrator would focus on the internal structure of the moons, surface composition, and surface strength and mechanical characteristics. The core payload would be a seismometer to study the internal structure of the moon, which would consume a third of the payload mass. A number of other instruments could also be added. One slide lists a possible instrument compliment that adds a mass spectrometer, accelerometer, thermal sensor, descent imager, and a magnetometer. The slide notes that including the descent imager could pose problems for the other instruments sampling the surface.

Not discussed in this presentation is a possible enhancement that would essentially be a mini-probe carried within the penetrator that has received some publicity lately (see thermal drill article). This would be a thermal drill that would melt and drill its way to depths as great as 10 m below the surface where the material should be free of chemical changes caused by radiation. The unit would be a small, self contained package that would leave the body of the penetrator but remain connected by wires for power and communications. A paper in Advances in Space Research is vague about what kinds of useful instruments could fit within the small body of the unit: “A melting system could sample waters which are transported into the instrument by the use of a micro-pump. A series of filters retains biogenic material, if present, for further analysis by an optical microscope, a chemical micro-laboratory or spectrometry. Gases, as indicators of biological activity, could be acquired by this combination of heating and drilling... Current GCMSs are not suited to be integrated into the thermal drill itself (due to size), but could eventually be mounted inside the penetrator... A wet experiment was developed for the Deep-Space-2 penetrators and tested in impact trials.”

Editorial Thoughts: Penetrators would significantly enhance the science return from these missions, and I hope they will be flown. As I understand it, neither ESA nor NASA are planning to pay for their development. Their inclusion into the mission would require another national space agency to fund the development. The presentation on penetrators was made by the Penetrator Consortium, a group of researchers located primarily in Britain. (The site has several interesting presentations on penetrator concepts for various solar system targets.)

The presentation at the EJSM conference and those at the consortium website suggest that the primary focus for now is on a penetrator for Ganymede. Analysis of for a Europa penetrator has several "to be determined" entries, with the key one probably being whether the penetrator's electronics could withstand the radiation dose as the orbiter maneuvers into Europa orbiter and then in Europa's orbit. It's hard enough to design electronics that can withstand slamming into an icy surface. Designing electronics that could also withstand the radiation may be too difficult. However, the metal body of the penetrator would provide some shielding and perhaps additional shielding could be carried by the orbiter (think of the penetrator and deorbit module inside a box or tube mounted on the orbiter).

Europa is a significantly smaller moon than Ganymede, and the deorbit module would be correspondingly smaller. The JEO orbiter is reserving 100 kg of mass for a possible penetrator. I wonder if the deorbit module might be enough smaller that JEO could carry two penetrators (assuming that the space can be found on the orbiter to house two penetrators).

And I am disappointed that there’s no mention of a surface camera. I understand the problems of including a deployable mast in a small penetrator. Still, it would be wonderful to see Jupiter in the sky above these moons.

Thursday, May 20, 2010

Two good articles have been published in the last few days. The first, from Air & Space magazine describes the proposed AVIATR Titan plane proposal. The article provides more background on this concept than I've seen before and provides images of the current design. (See this blog entry for a description and pictures of previous designs.) Unlike proposals for Mars airplanes, the AVIATR design doesn't require folded wings. Deployment following entry into Titan's atmosphere is gentle. “The clamshell’s heat-resistant bottom drops away, AVIATR is released, and the airplane noses into the airstream and levels off. Its speed at deployment is leisurely—a mere 25 mph. (A Mars airplane, by contrast, separates from its parachute at nearly the speed of sound, then has to unfold and begin flying in a matter of seconds. Lemke calls it the “death plunge.”)” You can check out the article at http://www.airspacemag.com/space-exploration/Titan-Air-.html#

The second article from the journal Nature describes the hope that the Falcon 9 launcher nearing it’s first test flight will fill a critical hole in NASA's plans. As I discussed in a previous blog entry, NASA will soon lose its workhorse moderate cost Delta II launcher. As the article states, “’We're almost reaching the stage of desperation for launch vehicles,’ says Jack Burns, a space scientist at the University of Colorado at Boulder and a member of NASA's science advisory committee. NASA science chief Edward Weiler adds, ‘If there is no replacement ever for the Delta II, that would take away a critical capability.’ He hopes that in three or four years the Falcon 9, developed by SpaceX of Hawthorne, California, will emerge as a low-cost replacement. ‘Very much hoping, I might add.’” The article is posted at http://www.nature.com/news/2010/100518/full/465276a.html

Correction: I should have also pointed out that the Nature article discusses Orbital Sciences' Taurus II launcher which could fill the gap for small lunar and planetary missions.

Saturday, May 15, 2010

Across the universe, plasmas are the dominant form of baryonic matter (that is the particles that make up the universe we can see and touch). Many missions have been flown to investigate the (magnetic) fields and (charged or ionized) particles within them, both around our own planet and around the sun and other planets. This blog entry continues the series that looks at contributions that the Europa Jupiter System Mission can make beyond the studies of the primary targets, Europa and Ganymede. Although this entry will touch upon those worlds since understanding the magnetic and radiation fields at those two moons are key to exploring them. The interaction of these moons with Jupiter's magnetosphere is a key method to explore their interior oceans, and the radiation delivered to Europa's surface may be a key source of energy to create the organic compounds that might enable life within its ocean.

Before I get too far into the topic, I'll be the first to admit that I lack the training in physics to properly understand this field, so I apologize if I don't go into depth (and for any mistakes I make). This is also not a topic that receives a lot of public attention. There's no pretty pictures (beyond auroras) and little that we can compare to our everyday lives. However, Jupiter offers an extreme laboratory to study magnetospheres and their plasmas. To quote from Wikipedia (http://en.wikipedia.org/wiki/Jupiter#Magnetosphere and http://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter):

"Jupiter's broad magnetic field is 14 times as strong as the Earth's... making it the strongest in the Solar System (except for sunspots). This field is believed to be generated by eddy currents — swirling movements of conducting materials—within the metallic hydrogen core. The field traps a sheet of ionized particles from the solar wind, generating a highly energetic magnetic field outside the planet — the magnetosphere. Electrons from this plasma sheet ionize the torus-shaped cloud of sulfur dioxide generated by the tectonic activity on the moon Io. Hydrogen particles from Jupiter's atmosphere are also trapped in the magnetosphere."

"The action of the magnetosphere traps and accelerates particles, producing intense belts of radiation similar to Earth's Van Allen belts, but thousands of times stronger. The interaction of energetic particles with the surfaces of Jupiter's largest moons markedly affects their chemical and physical properties. Those same particles also affect and are affected by the motions of the particles within Jupiter's tenuous planetary ring system. Radiation belts present a significant hazard for spacecraft and potentially to humans."

Both NASA's Jupiter Europa Orbiter and ESA's Jupiter Ganymede Orbiter will carry advanced sets of instruments for studying magnetic fields and their plasmas such as megnetometeris, plasma/energetic particle packages, UV spectrometers, plasma wave instruments, and ion/neutral mass spectrometers. The JGO spacecraft may also carry an energetic neutral atom (ENA) camera (http://en.wikipedia.org/wiki/Energetic_neutral_atom) to image particles within the magnetosphere similar to the instrument carried by the Cassini spacecraft at Saturn.

The true power of the mission, though, comes from having two spacecraft in orbit around Jupiter at the same time that can measure conditions at different places within the magnetosphere. That capability may be substantially enhanced with the addition of a dedicated Jupiter Magnetospheric Orbiter supplied by the Japanese JAXA space agency.

Sunday, May 9, 2010

My post on the Decadal Survey Update: Sticker Shock Ahead has resulted in several readers posting very thoughtful comments on how priorities should be set for planetary exploration. I encourage you to read them and post your own thoughts.

You may also want to read a post I did early in the year about how different the priorities would be if large missions are chosen versus a series of smaller missions. Check out My Stab at a Decadal Priority List. It explains my reasoning behind the lists that follow.

Here are the two lists I came up with:

Example of a priority list and budget for a program that emphasizes Flagship missions. Figures are in $Bs, and use either published estimates or my own best guesses. New Frontiers and Discovery figures include the PI budget (~$650M and ~$450M) plus launches and other overhead.

How I would prioritized my list of missions based on mission concepts that have been studied to date. This list recognizes that budgets may be cut, and has smaller missions that can substitute for larger missions or that can be enhanced if funding continues as currently planned. Since this list was published, I've learned of the AVIATR Titan plane proposal, and I would consider dropping another mission to fit it in (assuming that the technology is ready for flight, something hard for armchair mission planners to test).

There's of course nothing special about my list, and I publish them to stimulate thought and discussion. If anyone cares to send me their list, I will be happy to post it. Please do try to make it fit within the expected budget of $12.5 for the decade (not inflation adjusted). New Frontiers missions run about $1.4B and Discovery missions about $0.8B after all costs of launching, tracking, and overheads are included.

Saturday, May 8, 2010

The Mars III workshop was help at the end of March into early April. Unlike many conferences, this one didn't focus on the latest findings reported in 15-20 minute presentations. Instead, this workshop was a synthesis with a goal "to integrate the main results of both the recent Earth-based observations and the missions to Mars (MarsExpress, Mars Reconnaissance Orbiter, Phoenix and Mars Exploration Rovers) into a new global picture of Mars evolution." As such, the presentations that are posted are fantastic tutorials on a wide range of topics, from the geological history, to the climate, to the interior structure. Typical presentations (presumably with time for questions) lasted one-and-a-half hours. A series of hour long presentations on current and recently ended (Phoenix) missions and thirty minute presentations on future missions rounded out the program.

If you are interested in Mars, this is a great place to spend some time.

I found three slides in the introduction presentation by Jack Mustard, particularly interesting. The two following slides present key questions that dominated the field ten years ago and the key questions that dominate the field today. Note how little overlap there is. The past decade of exploration has done a great job of answering what had been the key questions, but of course that just led to new questions for the coming decade. The exception to this story was studies of the Martian interior which largely will remain on hold until a network of geophysical landers is eventually flown. (The presentation on network missions gives the long and sad history of attempts to get a network mission flown. Best current hope is for a mission around 2020, assuming that it once again is not bumped to fund higher priority missions.)

The third slide from Mustard's presentation provides the goals for exploration of the terrestrial worlds (which would in this context include the other half of our double world system, our own moon). All are key questions to understanding the evolution of our own world. I am beginning to feel that the goal for the next decade of exploration should be twin focuses on the terrestrial planets (with Mars receiving the bulk of the money and attention, but significant missions to Venus and/or the moon) and on the icy moons of Jupiter and Titan as possible abodes of life. Perhaps $5B to each set of missions, leaving ~$2B for Discovery class missions to asteroids and comets. While this would leave many missions I would very much like to see fly such as the Io Volcano Explorer and the Argo Neptune-Triton flyby, the success at Mars in answering a string of high priority questions in the past decade shows the power of focusing exploration.

Monday, May 3, 2010

Steven Squyres has been presenting updates at various planetary science conferences on the status of the Decadal Survey. The slide above is from his most recent presentation at an astrobiology conference. (You can down load the entire presentation by going to the Decadal Survey webpage and scrolling down to 'Past outreach events, and clicking on the 'Astrobiology Science Conference' presentation. Sorry, no url to the presentation itself.)

Other than these updates, formal news from the Survey has been scarce. Each of the working panels have been meeting over the past month in closed session to work on their reports. Several news articles, including one in the subscription only version of Aviation Week and Space Technology, have been touting the search for present and past life as an overarching theme likely to emerge from the Survey. (See a summary of the Aviation Week article here or the Space Daily article.)

Each of the science panels (inner planets, Mars, giant planets, etc.) has been including science goals that link to astrobiology (See slides at end of this blog entry from Squyres' presentation). For Mars and the outer planet satellites, this is easy since they include habitats that could be past or present abodes of life. For the inner planets and primitive bodies, the goal is to tie into the evolution of habitable worlds. Only the giant planets has not been able to find a tie to astrobiology.

The Aviation Week article lists several missions that best tie to an astrobiology theme; I've included possible costs that I've read in the past, but not Squyers' warning about sticker shock. (Note, for the purposes of the Survey, the decade runs from 2013 through 2022.)

Add this up, and assume 2-4 Discovery missions for those destinations without an astrobiology tie, and this would pretty well fill the expected budget of $12-13B over the decadal period (FY11 dollars).

One of Squyres' slides showed a schedule for the Survey's meetings. It showed that the results of the analyses of candidate missions will be available to the Survey in July of this year. It's not clear when those results will be made public.

I've gone through the list of missions under consideration by the Survey and listed them based on tie to an astrobiology theme. (Some of the missions listed as non-astrobiology could associated with some astrobiology theme. Feel free to disagree with my assignments!) Institutions listed after each candidate mission indicate which institution is preparing the analysis of that mission. Costs will be independently assessed.

In another area of Squyres' presentation, reemphasized that only missions that already flying or have formal new starts are excluded from the Decadal Survey's review. The missions in development that have formal new starts, plus the next New Frontiers selection (since the selection is in progress) are listed below:

The following slides are from Squyres' presentation and list the science goals of each sub-discipline (astrobiology goals are presumably highlighted since Squyres was presenting at an astrobiology conference).

About Me

You can contact me at futureplanets1@gmail.com with any questions or comments.
I have followed planetary exploration since I opened my newspaper in 1976 and saw the first photo from the surface of Mars. The challenges of conceiving and designing planetary missions has always fascinated me. I don't have any formal tie to NASA or planetary exploration (although I use data from NASA's Earth science missions in my professional work as an ecologist).
Corrections and additions always welcome.